1. Field of the Invention
This invention relates to a method and apparatus for producing a biased fabric in which the structural fibers are skewed from the fabric centerline. The method and apparatus hereof is particularly useful in producing a flimsy, woven, biased structural fabric in which the structural fibers are oriented about 45.degree. to the fabric centerline.
2. Background Description
Many types of structural fabrics are known, such as woven and nonwoven, biased and unbiased. Generally speaking, unbiased fabric has structural fibers running either parallel or perpendicular (or both) to the edges of the fabric. The configuration in which structural yarns run substantially parallel to the longitudinal edges and centerline of a flat, open-width, strip of fabric is called a "warp" configuration. The configuration in which the structural yarns run substantially perpendicular between the two longitudinal edges is called a "weft" configuration. Structural yarns may be held in place using secondary yarn or combined into a woven fabric having both weft and warp structural yarn. Fabric in which structural yarns are oriented at an angle skewed from the fabric centerline (neither parallel or perpendicular to the fabric centerline) is usually called a "biased" fabric.
Biased fabrics, particularly biased woven structural fabrics, have been found to have many advantages as a reinforcing structural material. For example, structural fiberglass fabrics can be combined with a thermosetting polyester resin to produce a fiberglass reinforced plastic. Such fiberglass reinforced plastic has many uses, such as in automobile bodies, aircraft fuselage, and marine craft.
Biased fabric is normally produced by processing a weft or warp knitted or woven fabric to skew the structural yarns. U.S. Pat. No. 4,567,738 illustrates an apparatus and method for producing a multi-layer nonwoven structural fabric. While various methods of producing a biased fabric have been useful in a variety of contexts, several types of material cannot be easily processed using known methods to produce a biased fabric. For example, many types of structural fabrics of interest are "flimsy" or "sleazy" in that the fabric is easily distorted by handling or even by its own weight if not supported. Such "flimsy" fabrics are particularly difficult to handle once the structural fibers are skewed from the weft or warp configuration. Therefore, using conventional methods it is difficult to maintain the integrity of the fabric during processing to produce a biased fabric.
Producing a biased structural fabric from such a sleazy starting fabric has become increasingly desirable in many applications, but has proven difficult to obtain using conventional fabrication techniques. Therefore, it would be a significant advance in the art if a method and apparatus were devised which could easily produce a biased structural fabric meeting precise product specifications, particularly where the starting fabric is a flimsy, sleazy, easily distorted fabric.